Lowpass filters are known in the art. One type of a lowpass filter is a Chebyshev filter that uses fixed values for its inductors and capacitors. Once the fixed values of the inductors and capacitors are selected, the cutoff frequency of the filter cannot typically be varied without changing components.
There are many applications in which it is desirable to have an RF lowpass filter which is tunable in cutoff frequency. It is also desirable for a lowpass filter to have high linearity such that a minimal amount of additional spurious are generated when subjected to an input spectrum with multiple tones.